X-ray installation



April 10, 1934. A, BQUWERS 1,954,612

x-RAY INSTALLATION Filed Aug. 8. 1929 2-Sheets-Sheet 1 /a N f j g r o af-f- 1 lucen/7501": eilerowwercm April 170, 1934. A. BOUWERS I 1,954,612

x-'RAY INSTALLATION Filed Aug. 8. 1929 2 Sheets-Sheet 2 Patented Apr.10, 1934 UNITED STATES PATENT OFFICE X-RAY INSTALLATION Eindhoven,

Netherlands, a limited-liability company of the Netherlands ApplicationAugust 8,

1929, Serial No. 384,400

In the Netherlands March 26, 1927 3 Claims.

An object of the present invention is to pro-` rI vide an arrangementadapted for carrying this principle into effect, which is Very simpleand practical.

Another object is to provide means with the aid of which, a shortexposure may be taken at any desired moment.

For carrying out the objects of the invention I have provided in anX-ray installation with an X-ray tube having an auxiliary electrodebetween the cathode and the anticathode, means for alternativelyimpressing on the auxiliary electrode a low potential that prevents thepassage of current across the tube and a higher potential allowing thedischarge of a condenser connected in parallel with the tube. As thisauxiliary electrode .30. use may be made of the usual device fordirecting the cathode rays on a limited portion of the anticathode, theso called focussing device.

Other objects and features will be apparent from the followingdescription considered in connection with the accompanying drawings, inwhich Figure 1 represents one embodiment of the invention and Figure 2 amodication employing a battery as the source of electrical energy.

In the drawings the primary side of a transformer is indicated by 1 andis connected to a suitable source of alternating current via theregulating resistance 3. The secondary winding 2 of thel transformer isconnected to the anode of a rectifying valve 4 the cathode of which isconnected to one of the plates of a condenser 5, the other plate beinggrounded. During the half cycles in which the anode of the valve 4 has apositive potential a current may flow unidirectionally to the condenser5. Discharge of the latter is not possible except through the X-ray tube6 which is connected across the condenser 5. The tube represented in thefigure has an incandescent cathode 8 and an anticathode 7 of the usualtype. Preferably, however, the anti- (Cl. Z50- 34) cathode isconstructed so as to be movable according to prior application Ser. No.186,522 of April 25, 1929. The outer wall of the tube comprises a metalportion 9 connected by fusion to glass parts by which it is insulatedfrom both electrodes of the tube. The incandescent cathode 8 issurrounded by an auxiliary electrode 10. The latter constitutes thefocussing device that directs the beam of cathode rays on a small areaof the anticathodes target. The auxiliary electrode lo and the groundedcathode 8 are connected to two contacts of a commutator 11.

In the position shown in the drawings the commutator gives groundpotential to the device 10, whereby the tube is rendered non-conductive,the electrons emitted by the cathode being retained by the space chargebetween the device 10 and the incandescent filament.

Meanwhile the condenser 5 .is gradually charged `up by the transformerin collaboration with the rectifier 4. At the moment at which the shortexposure should be made, the commutator 11 is turned to its oppositeposition connecting thereby the device 10 to a point of the transformerwinding 2 that has a potential lying between that of the anticathode andthat of the cathode. The device 10 then during a very short time gets apositive potential relative to the cathode and the electrostatic eldbetween these members is directed so as to impart an acceleration to theelectrons. The condenser now discharges via the X-ray tube.

It is also possible to use a battery for impressing the desiredpotentials on the device 10 instead of connecting the latter to thetransformer winding. An arrangement according to this modication isillustrated in Fig. 2, the arrangement being such 'that in the positionof commutator 11 shown in the drawings the positive pole of a battery 12is in connection with the cathode and the negative pole is in connectionwith device 10, the tube then being inoperative. In the other position,indicated in dotted lines, the connections with the battery areinterchanged and the electrostatic eld between device 10 and cathode 8is so as to permit the electrons to flow in the direction to theanticathode. In this arrangement the duration of the exposure depends onthe time of the commutator being in operative position or on thecapacity of the condenser together with the temperature of the filament.The passage of cur- It is obvious that, provided the condenser is in acharged condition, the operator is substantially free in choosing themoment at which the discharge shall take place.

No X-ray energy is emanated as long as the commutator remains in itsoperative position whereas the current in no time reaches its maximumValue when the commutator is turned over.

To some extent the focussing device plays con-I sequently the partfullled by the control grid in discharge tubes utilized in Wirelesstelephony and telegraphy.

What I claim is:

1. An X-ray installation for making short X-ray exposures, comprising atransformer, a storage condenser, and a rectier connected in series withthe secondary of said transformer, said transformer substantially fullycharging said condenser only over a plurality of cycles, an X-ray tubeconnectedl across said condenser and comprising a cathode, ananticathode and an auxiliary electrode, and means for impressing on theauxiliary electrode a low potential for preventing the passage ofcurrent across said tube, and a higher potential for causing thedischarge of the condenser.

2. An X-ray installation for making short X- ray exposures, comprising atransformer, a storage condenser, and a rectifier connected in serieswith the secondary of said transformer, said transformer substantiallyfully charging said condenser only over a plurality of cycles, an X- raytube connected across said condenser and comprising a nlarnentarycathode, an anticathode, and an auxiliary electrode, and means forimpressing on the auxiliary electrode the same potential as that of aportion of the cathode for preventing the passage of current across thetube, and a higher potential for causing the discharge of the condenser.

3. An X-ray installation for making short X- ray exposures, comprising atransformer, a storage condenser, and a rectier connected in series withthe secondary of said transformer, said transformer substantially fullycharging said condenser only over a plurality of cycles, an X-ray tubeconnected across said condenser and comprising a cathode, an antioathodeand a focussing device for directing the cathode rays on a limitedsurface of the anticathode, and means for impressing on said device alow potential for preventing the passage of current across said tube,and a higher potential for causing the discharge of the condenser.

ALBERT BOUWERS.

